RADIONUCLIDE IMAGING OF THE SKELETON: RADIOPHARMACEUTICALS Flashcards
Technetium-99m MDP
Ideal characteristics of a radiopharmaceutical?
- inexpensive
- stable
- rapidly accumulate at the target
- quickly clear from background tissues
- have favorable imaging and dosimetry characteristics
Why is technetium-99m (Tc-99m) commonly used for single-photon gamma camera imaging?
due to its desirable 140 keV gamma photon and 6-hour half-life, which make it well-suited for imaging with good resolution and patient safety.
What is the significance of the 511-keV annihilation photons in PET imaging
In PET imaging, the radiopharmaceuticals emit two 511-keV annihilation photons that travel at 180 degrees from each other, which are detected to create high-resolution images.
Why is fluorine-18 commonly used in PET imaging?
Fluorine-18 is commonly used because its 109.8-minute half-life is short enough to minimize patient dose, yet long enough to allow for production, distribution, and completion of the exam.
What is the purpose of combining technetium-99m (Tc-99m) with a phosphate analog carrier molecule in bone imaging?
The combination allows the agent to demonstrate skeletal turnover by localizing to the bone, which helps assess bone activity and disorders.
What was the initial radiopharmaceutical used for bone imaging, and what was its characteristic bond?
The initial radiopharmaceutical used was technetium-99m pyrophosphate (Tc-99m PYP), characterized by its P–O–P bond.
Why are diphosphonate structures preferred over pyrophosphates in bone imaging radiopharmaceuticals?
Diphosphonate structures have a more stable P–C–P bond, allowing for faster background clearance through renal excretion, which improves imaging quality.
Name two diphosphonate-based radiopharmaceuticals used in bone imaging.
Technetium-99m hydroxymethylene diphosphonate (Tc-99m HMDP or HDP) and technetium-99m methylene diphosphonate (Tc-99m MDP).
Between Tc-99m HMDP and Tc-99m MDP, which is more commonly used in bone imaging and why?
Tc-99m methylene diphosphonate (Tc-99m MDP) is more commonly used due to its practical advantages and higher usage in clinical settings.
